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Full text of "The jumping bean - Emporia melanobasis, Hmpsn"

\3 Biodiversity 
^Heritage 
^^Library 

http://www.biodiversitylibrary.org/ 



South African journal of natural history. 

Pretoria,South African Biological Society. 
http://www.biodiversitylibrary.org/bibliography/7396 



v. 2 (1920): http://www.biodiversitylibrary.org/item/31375 
Page(s): Page 121, Page 122, Page 123, Page 124 



Contributed by: MBLWHOI Library, Woods Hole 
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THE JUMPING BEAN t2L 



The Jumping Bean — Emporia melanobasis, Hmpsn. 

By A. T. Jaxse. 

The Jumping Bean is too well known to make it 
necessarv to describe the external form of the seed. It 
is not a beau at all, hut the schizocarp of a plant belong- 
ing to the Euphorbiareae. It is by no means confined m 
s. Africa, bnl occurs also in X. America and S. Europe, 
in fact it was known from Europe as early as the be- 
ginning of the sixteenth century, but it does not seem 
to have attracted as much attention then as it has done 
during* the last years. In 1854 a "jumping bean", re 
sembling in every respect The one found in South Africa. 
was found in Mexico and well studied by the well-known 
entomologist Lucas, whose observations are very con 
elusive. It was onlv since 1800. however, when these 
"beans *' were imported from Mexico in such large uian- 
tities, that they became more known by the public that 
bought them from mere curiosity. And no wonder! The 
jumping of these beans is a mosl weird spectacle. This 
peculiar movement in the seed is caused by the larva of 
a moth. 

The Mexican ''beans" develop a small moth, thai: 
belongs to the Tortricidae and is named bv Westw. as 
Oarpocapsa salfitaas. This genus has in Europe six 
species, all of which live inside fruit, which they all 
leave however before pupation, while the Mexican species 
pupates also inside the fruit. 

The jumping beans from South Africa also pupate 
inside the "bean", ai least the species known to me, 
and the one I know from the Transvaal resembles in 
many respects the Mexican jumping bean. 

The Transvaal "jumping bean M is clearly the fruit of 
a Euphorbiaceae, and comes from the Lvdenbunr d^'rict 



122 



MR. A. T. JAXSE 



but I have never had the opportunity of seeing more of 
the plant than the "beans". It seems that all the fruit 
are inhabited by the larvae, as a sound seetl never came 
to my notice nor to the notice of the collectors who sent 
the "beans" on to me. I also received far too little 
material to ask the help of a specialist to identify the 
plant that produces the fruit. As the generic characters 
of this family are founded on the structure of the seed, 
however, it will be impossible to identify the genus ex- 
cept approximately. 

The larvae that I found inside differed very little from 
other larvae that live inside plant parts, except that H 
was very thick in the middle probably due to abnorma 1 
development of the muscular system in that region. 
When taken out of the "bean*', it always maintained a 
semi-circular position, and the size was certainly too 
big to allow the full grown larva to stretch itself when 
inside the "bean". This fact I think of great important-- 
in the explanation of the jumping power of the larva. 
When the larva came to me they were full grown and 
the fruit consisted of the empty shell only, yet they re 
mained in this larval stage from November 23rd, 1908, 
till June next year, when 1 found the first pupa inside 
those "beans" that did not jump any more. Some of 
them even pupated as late as October the 8th, or nearly 
a year after being apparently full grown. During the 
larval stage the "beans" jumped every now and then, 
often to a height of noi less than an inch, and when left 
by themselves in an open shallow box for some days thev 
would all gradually disappear. When about a hundred 

were confined in a cardboard box they would keep up i 

rattling noise, that never quite ceased, but that became 
more pronounced when the box was exposed to heat, r 
often observed that some of them kept on jumping every 
two or three seconds for several minutes when a shorl 
period of rest would be enjoyed, to begin the jumping 
again, especially when the temperature was rather hiffh. 
One naturally asks the use of this movement, but I must 






THE JUMPING DEAN 12*' 

confess, thai 1 cm n not think of any use that would 
justify such a considerable waste of energy, but it still, 
more surprises me thai the larva can keep up this move- 
ment Tor several months without any food, not to speak 
of the quantity of fund necessary to bring the young 
larva to maturity, not more than about twice its own 
volume being stored in the fruit. The fruit when sent 
to me weii 1 quite sound on the outer surface, not one 
opening or mark of en nance could he detected by me 
even with a magnifyer, so I presume that the larva must 
enter the fruit when the latter is still very young and 
that the larva feeds on the food brought there by tin 
plantparts concerned, allowing at the same time s 
cient food for the proper growth of the outer shell, or the 
moth must have a means of depositing the eggs into the 
tissue when the fruit is nearly full grown, but I could not 
find in (lie female moths that hatched out any ovipositor 
that even suggested its capability of performing this. 
Before pupation (lie larva cuts a very neat circular hole 
in the hardest part of the shell, without removing the 
centre, but this lid is only visible with the aid of a 
magnifyer and seems to he kept in its place from the 
inside by a silken surface that covers in fact the whole 
inside One to two months after these 1 lids are made the 
moths emerge and in mv beans thev all were of one species 
belonging to the Pyralidae family of the genus Tepkris. 
The species was before quite unknown to me and most 
probably new, but the peculiar thing is that the " jump- 
ing beans" of other countries contain larvae of moths be- 
longing to other families. The Mexican species is a 
Tortria?, the Transvaal species a Pyralid and the other I 
know from Table mountain is a Timid. This last species 
is described by Merrick as Scirotis a thief (t, the only 
speeies known of this genus. 

As Mr. Meyrick rightly says, these " : beans'' have 
nothing whatever to do. with the ^ beans " from Mexico 
(nor from those of Lydenburgi, as far as relationship is 
concerned but are more to be looked upon as special ways 



121 



MR. A. T. JANSE 




of pupation. That the Cape species has parasites need 
not surprise us, since the larvae live for some time outside 
the seed, but it is more peculiar that many of my 
specimens, that I have every reason to helieve to have 
lived nearly, if not all, their time inside the fruit, had 
Hymen op tenuis parasites, that bored their way through 
the thick shell in quite a different manner to that of the 
moth. I think that those Ichneumons bring their eggs 
intu the larvae by boring with their ovipositor into the 
shell in such a way that the opening is afterwards in- 
visible. 

It was not so much why the larva jumped so frequently 
but hoir they could perform tins feat which required 
such a large amount of muscular power, that puzzled me 
most. I partly opened several and observed it carefully, 
in the act of jumping, and I feel sure that the larva first 
contracts itself, then suddenlv stretches itself as much 
as space allows so as to throw, as it were, the two ends 
of its body against those walls of the beau that are up- 
wards, at the same time raising itself, and this I ^hink 
forces the "bean'' up for sometimes the height of an 
inch. Mr, Lucas made verv careful observations on the 

* 

Mexican bean, however, and comes to somewhat different 
conclusions. In order to observe the larva well, he took 
one of the tlat walls awav and placed a small niece of 
mica in its place. He then found that the larva climbs 
on to the highest wall, stretches itself till lie- ends »(' its 
body are at the corner of tin* bean then it contracts its 
body so that the larva begins to swell, then the body 

stretches suddenly in the direction of the upper part of 

the bean and this causes the bean to move in one direc- 
tion. 

1 would not like to deride which of .the lw<> is the most 
probable explanation; j>erhaps there are even several 
means of producing (lie same thing: the uncanny niove- 

nirhof what is apparentlv bin a snn].